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Saturday, 4 June 2011

Planning an organic vegetable garden

The Vegetable Plot

The best site for a vegetable plot is one that enjoys the most sunshine and where shade, slopes or exposure to strong winds is minimised. If you happen to encounter these problems there are however remedies such as laying your beds across rather than down a slope to avoid soil washing-away and introducing living wind breaks by hedging.

I would recommend a north-south bed system rather than planting in rows for your plot. The narrow bed system has many advantages: it makes crop rotation more straightforward; all work is done from permanent paths and so avoids compacting the soil by treading which helps soil structure and fertility; manuring, liming and composting are concentrated where sowing and planting will take place; the soil depth can be increased and plants can be placed closer together which will increase yields and reduce the space for weeds to grow.  

The width of your beds is dependant on the size of your vegetable plot but it is worthwhile ensuring a width which allows you to reach from the path to the centre of a bed without over-stretching . Beds can vary from about 90cm to 150cm wide and can be of any length. We have settled for twenty-two beds which are 150cm wide and 6 metres long. Our beds are at ground level, rectangular in shape with straight sides and have a gentle curve outwards from the centre. But you can design beds of the shape, width, length and height you find most useful. If you wish to have beds elevated off the ground there are a wide range of edging materials from stone to timber which will enable you to do so.

Paths should be firm and kept weed free and at a minimum of 40cm wide but, if space permits, leave some paths at 90cm to allow access for wheelbarrow to transport manure and compost. If you wish to avoid the need for path weeding a heavy-duty water permeable black fabric could be used and covered with straw or any other material readily accessible. 

Crop Rotation

If you grow the same crop in the same space each year you will allow diseases specific to a particular crop to build in your soil and you will also deplete the soil of essential nutrients, as different crops vary in their soil nutrient requirements. By following a crop rotation system you will reduce the risk of diseases and ensure soil nutrient levels recover before a crop is again grown in the same space. There are various crop rotation systems but most ensure that nutrients left by the previous crop are utilised by the crop which follows.

The main principles of crop rotation are: (a) that the potato and cabbage families should have the largest possible gap before re-occupying the same ground because the potato family do not like lime but the cabbage family do and the two families should, therefore, be at opposite ends of the cycle; (b) the root family prefer soil which has not been recently manured to avoid vegetables forking and finally (c) it is important to keep the same family together as they have similar nutrient requirements.

I would recommend the following 4 Year Rotation System as it provides a greater gap between the potato and cabbage families than the 3 Year Cycle. Whichever system you use, it is vital to keep notes as by year two or three it would be impossible to remember what was planted where. Whether you simply divide your vegetable plot into four beds or have twenty beds the same principles apply. And finally do not worry if you cannot adhere rigidly to any rotation plan, as long as you avoid planting the same family in the same plot in consecutive seasons then you are helping your soil. 

Year 1Year 2Year 3Year 4
 Plot 1(A)Manure heavily before planting Potato Family.  (B)Lime heavily before sowing legumes. Mulch with compost and then more liming (C)Cabbage
(D) Onion and Root Family.
Ideally manured a few months before sowing
 Plot 2BC     DA 
 Plot 3C    AB
 Plot 4DA

The Cucurbitaceae Family (cucumbers, marrow, squash and pumpkin) and sweetcorn, spinach, beetroot and jerusalem artichokes which do not fit into any of the above groups can be used to fill gaps wherever they appear.

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